The present invention relates to a suction valve built in an endoscope, especially an endoscope for medical use.
In general, the endoscope for use in the medical inspection of the somatic cavity and others is equipped with a suction mechanism for sucking up filthy matters, mucus and others staying in the somatic cavity. The suction mechanism of this kind is equipped with a suction path, of which one end opens as a suction inlet at the tip distal end of the insertion portion of the endoscope and the other end side is connected with a negative pressure generation source. If it is required to remove filthy matters, mucus, body fluids and others left in the somatic cavity, the negative pressure generation source operates to make a negative pressure suction force act on the inside of the suction path, thereby sucking up filthy matters, mucus and others staying in somatic cavity through the suction inlet at the tip distal end of the endoscope.
Now, referring to FIG. 7 schematically showing the constitution of the entirety of an endoscope, this endoscope 200 is constituted such that an insertion portion 204 is connected with a control portion 202 while a universal cord 206 branching off the control portion 202 is connected with the negative pressure generation source (not shown) and a light source device (not shown) as well.
The insertion portion 204 is provided with an insertion channel 208 capable of transferring medical treatment tools for instance a forceps and others for the exclusive endoscope use therethrough. The treatment tool insertion channel 208 is in communication with a treatment tool inducing inlet 210 which opens to the control portion 202.
As the treatment tool insertion channel 208 can be used also as a suction path, the tip opening of it is able to function as a suction inlet. This treatment tool insertion channel 208 joins to a suction side path 212 at a certain point inside the control portion 202.
The suction side path 212 communicates with a suction source side path 214 through a suction valve 216 provided in the control portion 202. In this way, a suction route is formed by the treatment tool insertion channel 208, the suction side path 212, and the suction source side path 214. The suction source side path 214 is provided inside the universal cord 206 and connected with the negative pressure source (not shown).
The suction valve 216 is a valve for controlling the change of the connection between the suction side path 212 and the suction source side path 214. FIG. 8 indicates an example of the constitution of the valve of this kind.
The suction valve 216 includes a valve casing 218 fitted to the control portion 202 of the endoscope 200, and a valve member 220 which is set up in the valve casing 218 so as to make a sliding motion in response to the push-down motion of a button 221.
An active blockade face 222 is formed in the outer peripheral surface around the lower part of the valve member 220 while a side through-hole 224 is formed on the upper side of the active blockade face 222. The bottom portion of the valve member 220 is kept open and communicated with the above side through-hole 224.
The suction side path 212 and the suction source side path 214 are connected together with the valve casing 218. With the sliding motion of the valve member 220, the suction side path 212 comes to communicate with the suction source side path 214 through the side through-hole 224 of the valve member 220, and it is cut off from the suction source side path 214 by the active blockade face.
As long as the endoscope is being used, the negative pressure generation source (not shown) is continuously kept in the powered condition. On one hand, while no suction control is carried out, the button 221 is not push downward as shown in FIG. 8. Consequently, the suction side path 212 is cut off from the suction source side path 214 by the active blockade face 222 of the valve member 220 while the negative pressure source comes to communicate with the atmosphere through the suction valve 216. To put it more concretely, the suction source side path 214 comes to communicates with the atmosphere through the side through-hole 224, an opening 232a formed in a spring seat member 232 for supporting a spring 226 energizing the button 221 and an air releasing groove 236, respectively. With this constitution, the suction inlet in communication with the suction side path 212 is held substantially in the non-loaded condition.
When executing the suction control, the valve member 220 of the suction valve 216 is pushed downward by using the hand fingers to make it slide downward along the casing 218. With this downward-motion of the valve 220 as shown in FIG. 9, the suction side path 212 comes to communicate with the suction source side path 214 through the side through-hole 224 of the valve member 220, thereby the negative sucking pressure generated by the negative pressure generation source coming to act on the suction side path 212.
In the suction valve for use in the endoscope of this kind, however, even if no suction control is carried out as shown in FIG. 8, it takes place under certain circumstances that foreign substances such as filthy matters, mucus, body fluids and others stick to the active blockade face 222 of the valve member 220. If the valve member 220 is moved to slide along the casing 218 as shown in FIG. 9, it takes place that the foreign substances like the above-mentioned comes in a slide portion, that is, a very narrow gap between the valve casing 218 and the active blockade face 222 of the valve member 220. This causes such a problem that the slide friction becomes large in the tiny gap between the valve casing 218 and the active blockade face 222 of the valve member 220.
Consequently, if the above slide friction becomes larger than the restoration force of the spring 226 prepared as means for energizing the valve member 220, it becomes hard for the valve member 220 to go back to its original position, which makes the smooth suction control impossible, eventually.
Accordingly, the invention has been made in view of the above-mentioned problem, and an object of it is to provide a novel and improved suction valve for use in the endoscope, which is able to make the suction switch control more stable and smooth.